1/*-------------------------------------------------------------------------
2 *
3 * itemptr.c
4 * POSTGRES disk item pointer code.
5 *
6 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 *
10 * IDENTIFICATION
11 * src/backend/storage/page/itemptr.c
12 *
13 *-------------------------------------------------------------------------
14 */
15#include "postgres.h"
16
17#include "storage/itemptr.h"
18
19
20/*
21 * ItemPointerEquals
22 * Returns true if both item pointers point to the same item,
23 * otherwise returns false.
24 *
25 * Note:
26 * Asserts that the disk item pointers are both valid!
27 */
28bool
29ItemPointerEquals(ItemPointer pointer1, ItemPointer pointer2)
30{
31 /*
32 * We really want ItemPointerData to be exactly 6 bytes. This is rather a
33 * random place to check, but there is no better place.
34 */
35 StaticAssertStmt(sizeof(ItemPointerData) == 3 * sizeof(uint16),
36 "ItemPointerData struct is improperly padded");
37
38 if (ItemPointerGetBlockNumber(pointer1) ==
39 ItemPointerGetBlockNumber(pointer2) &&
40 ItemPointerGetOffsetNumber(pointer1) ==
41 ItemPointerGetOffsetNumber(pointer2))
42 return true;
43 else
44 return false;
45}
46
47/*
48 * ItemPointerCompare
49 * Generic btree-style comparison for item pointers.
50 */
51int32
52ItemPointerCompare(ItemPointer arg1, ItemPointer arg2)
53{
54 /*
55 * Use ItemPointerGet{Offset,Block}NumberNoCheck to avoid asserting
56 * ip_posid != 0, which may not be true for a user-supplied TID.
57 */
58 BlockNumber b1 = ItemPointerGetBlockNumberNoCheck(arg1);
59 BlockNumber b2 = ItemPointerGetBlockNumberNoCheck(arg2);
60
61 if (b1 < b2)
62 return -1;
63 else if (b1 > b2)
64 return 1;
65 else if (ItemPointerGetOffsetNumberNoCheck(arg1) <
66 ItemPointerGetOffsetNumberNoCheck(arg2))
67 return -1;
68 else if (ItemPointerGetOffsetNumberNoCheck(arg1) >
69 ItemPointerGetOffsetNumberNoCheck(arg2))
70 return 1;
71 else
72 return 0;
73}
74